CN112689748B

CN112689748B - Hydraulic diaphragm seal and pressure transducer having a hydraulic diaphragm seal

Info

Publication number: CN112689748B
Application number: CN201980060034.0A
Authority: CN
Inventors: 帕特里克·多里亚
Original assignee: Endress and Hauser SE and Co KG
Current assignee: Endress and Hauser SE and Co KG
Priority date: 2018-09-24
Filing date: 2019-08-15
Publication date: 2023-06-02
Anticipated expiration: 2039-08-15
Also published as: CN112689748A; WO2020064213A1; DE102018123433A1; US11668617B2; EP3857196A1; US20220003624A1; EP3857196B1

Abstract

A diaphragm seal for transmitting pressure of a process medium, the diaphragm seal comprising: a body (1) having a surface (2); and a separation membrane (3) fixed to the surface (2) and forming a pressure chamber (4) between the separation membrane and the surface, the pressure chamber being in communication with a hydraulic passage (5) via an opening (6) in the surface, the separation membrane being capable of being exposed to the process medium on a first separation membrane side (33), the pressure chamber and the hydraulic passage being filled with a transmission fluid (7) for transmitting the pressure of the process medium; the isolation diaphragm is a planar diaphragm having a peripheral rim (32) and is bonded to the main body in a pressure-tight manner by a single peripheral weld (10), and the isolation diaphragm has a central intermediate region (12), wherein the diaphragm seal comprises a temperature transducer (20) for determining a temperature measurement variable of the process medium, the temperature transducer being fixed in said intermediate region on a second isolation diaphragm side (34) of the isolation diaphragm, and the main body being bonded to the isolation diaphragm such that the transmission fluid is not in contact with the temperature transducer.

Description

Hydraulic diaphragm seal and pressure transducer having a hydraulic diaphragm seal

Technical Field

The present invention relates to a hydraulic diaphragm seal and a pressure transducer having a hydraulic diaphragm seal.

Background

The hydraulic diaphragm seal generally includes a body having a surface to which a diaphragm having at least two welds is secured in a pressure-tight manner, such that a pressure chamber is formed between the diaphragm and the surface, and the pressure chamber communicates with a hydraulic passage via an opening in the surface of the body. The pressure chamber and the hydraulic passage are filled with a transmission fluid.

In general, knowledge of process temperature is critical to controlling an industrial process. When using hydraulic diaphragm seals, the process temperature is usually detected by two different possibilities. In a first possibility, the change in resistance of a resistor in the pressure transducer is used to determine the process temperature, while in a second possibility a temperature transducer formed separately from the pressure transducer is used to determine the process temperature.

However, both of these possibilities have the disadvantage that real-time temperature detection is not possible due to the inertia of the transport fluid.

As long as the temperature-dependent deformation of the diaphragm during the pressure measurement is accompanied by a diaphragm error, it is equally important for accurate pressure measurement to know the temperature of the diaphragm seal in the region of the pressure chamber or diaphragm and thus the temperature of the process as precisely as possible. Solutions known from the prior art have a temperature transducer arranged in the vicinity of the isolating membrane or introduced from the back into the body of the diaphragm seal in order to measure the temperature of the body in the vicinity of the pressure chamber. These sensor positions are in principle error-prone, since the thermal mass of the body prevents the body temperature from immediately adapting to the temperature of the transmission fluid in the pressure chamber, which can vary very rapidly due to rapid medium temperature changes and convective heat transfer through the flowing medium. Instead, a temperature transducer arranged in the vicinity of the separating membrane and optionally in contact with the medium requires an additional opening in the medium container or medium carrying line through which the temperature transducer can be inserted, or in the case of a given separating membrane area, the radius of the body must be enlarged by such a value that there is still room on the edge of the body for the temperature transducer to be mounted in the vicinity of the separating membrane.

The same design problem arises if, in other measurement tasks, in addition to the process pressure, a second sensor is to be used to detect a second measurement variable. This means that space for mounting the second sensor must be provided again.

Disclosure of Invention

It is therefore an object of the present invention to provide a diaphragm seal and a pressure transducer with a diaphragm seal, which overcome the mentioned disadvantages of the prior art.

According to the invention, this object is achieved by a diaphragm seal according to the first aspect of the invention and a pressure transducer according to the second aspect of the invention.

The diaphragm seal according to the invention for transmitting the pressure of a process medium comprises:

a body having a surface;

and a separation membrane fixed to the surface and forming a pressure chamber between the separation membrane and the surface, the pressure chamber being in communication with a hydraulic passage via an opening in the surface, the separation membrane being capable of being exposed to the process medium on a first separation membrane side, the pressure chamber and the hydraulic passage being filled with a transmission fluid for transmitting said pressure of the process medium; the barrier film is a planar film having a peripheral edge and bonded to said surface of the body in a pressure tight manner by a single peripheral weld, and the barrier film has a central intermediate region; wherein the diaphragm seal further comprises a temperature transducer for determining a temperature measurement variable of the process medium, the temperature transducer being fixed in an intermediate region on a second isolation diaphragm side of the isolation diaphragm opposite the first isolation diaphragm side, and the body being bonded to the isolation diaphragm in the intermediate region such that the transmission fluid is not in contact with the temperature transducer.

An advantageous embodiment of the diaphragm seal according to the invention provides that the temperature transducer is bonded to the diaphragm on the second diaphragm side in the intermediate region by a thermally conductive layer. The thermally conductive layer can be formed, for example, from a thermally conductive adhesive, a soft solder connection, or a thermally conductive paste. Preferably, the thermal conductivity of the thermally conductive adhesive in the hardened state is greater than 0.1, preferably greater than 0.5W/(m·k). The thermally conductive paste preferably has a thermal conductivity of 0.8 to 10W/(mK). The solder layer preferably has a thermal conductivity greater than 50W/mK.

A further advantageous embodiment of the diaphragm seal according to the invention provides that the body has a continuous central recess (in particular a hole) into which the temperature transducer is inserted from the back of the body facing away from the medium. In particular, this embodiment may provide that the gap between the temperature transducer and the wall of the central bore is at least partially covered with a thermally insulating material, preferably a thermally insulating material other than air.

A further advantageous embodiment of the diaphragm seal according to the invention provides that the body is bonded to the isolating diaphragm in the intermediate region by a peripheral adhesive connection, so that the transmission fluid is not in contact with the temperature transducer. Preferably, an epoxy adhesive is used as the adhesive for the adhesive joint, which has a smaller or approximately the same coefficient of thermal expansion as the surrounding body and/or less interaction with the transport fluid.

A further advantageous embodiment of the diaphragm seal according to the invention provides that the main body and the isolating membrane (3) each have a metallic material.

A further advantageous embodiment of the diaphragm seal according to the invention provides that the separating diaphragm has a deflectable working area between a peripheral line delimiting the intermediate area and a peripheral rim, and that at least one peripheral bead is arranged between the peripheral line and the peripheral rim.

A further advantageous embodiment of the diaphragm seal according to the invention provides that the peripheral adhesive connection is applied between a peripheral line defining the intermediate region and the central recess, in particular the hole.

The pressure transducer according to the invention comprises a diaphragm seal according to the invention and a pressure measuring unit which is able to withstand said pressure of the process medium via the hydraulic passage of the diaphragm seal, and an electronic circuit for generating a regulated pressure-related signal from the main signal of the pressure measuring unit.

In an advantageous embodiment of the pressure transducer, it is provided that the electronic circuit comprises means for processing signals for temperature measurement variables in the temperature transducer. In particular, this embodiment may provide that a signal of the temperature transducer is present at the input of a correction circuit for correcting a temperature error of the pressure-related signal.

A further advantageous embodiment of the pressure transducer according to the invention provides that the pressure transducer is an absolute pressure transducer, a relative pressure transducer or a differential pressure transducer.

Drawings

The invention is explained in more detail with reference to the following figures. The following figures are shown:

fig. 1: a longitudinal section of a pressure transducer according to the invention; and

fig. 2: a diaphragm seal according to the invention, which is part of a pressure transducer, is part of a longitudinal section.

Detailed Description

The pressure transducer shown in fig. 1 comprises a body 1 having a surface 2, a disc-shaped isolating membrane 3 being fixed to the surface 2 on its peripheral edge 32 with a single peripheral weld, whereby a pressure chamber 4 is formed between the body and the isolating membrane 3. The separator 3 of this exemplary embodiment has two peripheral beads (beads) 19. A bore extends through the body 1 from the pressure chamber 4 to form a hydraulic passage and to transfer pressure to a pressure receiver. In order that the pressure can also be transferred correspondingly, the pressure chamber is filled with a transfer fluid 7 (e.g. oil).

In other words, the components described so far relate to a diaphragm seal module which is combined with a pressure measuring unit to form a pressure transducer according to the invention. The pressure measuring cell comprises a carrier 111 to which the piezoresistive pressure measuring element 11 is fixed. The pressure measuring unit can be designed as a relative pressure measuring unit, a differential pressure measuring unit or an absolute pressure measuring unit. In the embodiment shown in fig. 1, the pressure measuring unit is designed as a relative pressure measuring unit. In this case, the pressure to be measured is applied to the pressure measuring unit via a channel 112 which is integrated in the carrier 111 and is coupled to the aperture by the body. For this purpose, the pressure measuring unit 11 serves as a pressure receiver for the hydraulic passage realized by the bore and the channel 112.

The main signal of the pressure measuring cell 11 is first pre-processed by the circuitry on the circuit board 14 and then further conditioned and post-conditioned communicated via a common protocol, such as 4 to 20mA or digital fieldbus protocol.

Furthermore, the pressure transducer according to the invention comprises a temperature transducer 20 which is introduced into the central bore 8 through the body 1 of the diaphragm seal module until the backside, i.e. the side of the isolating membrane facing away from the process medium, detects the temperature of the process medium. In this case, a central hole means a hole extending along a rotation axis, which is related to the outer contour of the body. Since the temperature transducer 20 is not in direct contact with the process medium, contamination of the medium by the temperature transducer 20, corrosion of the temperature transducer and interactions between the medium and the temperature transducer 20 can be avoided, making this design particularly suitable for sanitary applications and/or corrosive chemicals. In order to be able to reliably determine rapid temperature changes of the process medium, the temperature transducer is glued to the back side of the isolating membrane 3 by means of a thermally conductive adhesive 15, thereby providing a good thermal coupling. The isolation diaphragm preferably has a very small thickness in the range of about 20 to 60 μm so that the temperature transducer 20 can detect substantially real-time fluctuations in the temperature of the process medium. In order to thermally decouple the temperature transducer 20 from the transmission fluid, the isolating membrane 3 is bonded to the body in an intermediate region 12, which extends around the rotation axis 18. This can be done, for example, by means of a specific adhesive, which has a lower thermal conductivity than the thermally conductive adhesive, through the peripheral adhesive layer or the adhesive connection 13. Furthermore, in order to also thermally isolate the temperature transducer 20 from the body, an insulating material 9 may be introduced into the gap between the bore wall 81 and the temperature transducer 20.

The main signal of the temperature transducer (e.g. PT1.000 sensor) is supplied via the wire 17 to the circuit board 14, thereby being adjusted to a measurement signal and optionally to the main signal used to compensate the pressure transducer.

List of reference numerals

1. Main body

2. Surface of the body

3. Isolation film

31. Peripheral line

32. Peripheral edge

33. First side of the isolation film

34. Second side of the isolation film

4. Pressure chamber

5. Hydraulic passage

6. An opening

7. Transport fluid

8. Hole(s)

81. Pore walls of pores

9. Heat insulating material

10. Weld joint

11. Pressure measuring unit

111. Carrier body

112. Channel

12. Intermediate region

13. Peripheral adhesive attachment

14. Electronic circuit

15. Thermally conductive adhesive

16. Correction circuit

17. Electric wire

18. Axis of rotation

19. Hemming

20. Temperature transducer

Claims

1. A diaphragm seal for transmitting pressure of a process medium, the diaphragm seal comprising:

-a body (1) having a surface (2);

and an isolating membrane (3) fixed to the surface (2) and forming a pressure chamber (4) between the isolating membrane and the surface, the pressure chamber being in communication with a hydraulic passage (5) via an opening (6) in the surface, the isolating membrane (3) being exposable to the process medium on a first isolating membrane side (33), the pressure chamber (4) and the hydraulic passage (5) being filled with a transmission fluid (7) for transmitting the pressure of the process medium; the isolating membrane (3) is a planar membrane having a peripheral rim (32) and is bonded to the surface (2) of the body (1) in a pressure-tight manner by a peripheral weld (10), and the isolating membrane (3) has a central intermediate region (12), wherein the diaphragm seal further comprises a temperature transducer (20) for determining a temperature measurement variable of the process medium, which temperature transducer is fixed in the intermediate region (12) on a second isolating membrane side (34) of the isolating membrane (3) opposite the first isolating membrane side (33), and the body (1) is bonded to the isolating membrane (3) in the intermediate region (12) such that the transmission fluid (7) is not in contact with the temperature transducer (20).

2. The diaphragm seal of claim 1, wherein the temperature transducer (20) is bonded to the isolation diaphragm by a thermally conductive layer (15) in the intermediate region on the second isolation diaphragm side.

3. Diaphragm seal according to claim 1 or 2, wherein the body (1) has a continuous central recess into which the temperature transducer (20) is inserted from a back side of the body (1) facing away from the medium.

4. A diaphragm seal according to claim 3, wherein the central recess is a central aperture (8).

5. Diaphragm seal according to claim 4, wherein the gap between the temperature transducer (20) and the bore wall (81) of the central bore (8) is at least partially covered with a heat insulating material (9).

6. The diaphragm seal of claim 4, wherein the body is bonded to the isolation diaphragm in the intermediate region by a peripheral adhesive connection such that the transfer fluid (7) is not in contact with the temperature transducer (20).

7. The diaphragm seal according to claim 1 or 2, wherein the main body (1) and the isolation diaphragm (3) each comprise a metallic material.

8. The diaphragm seal according to claim 6, wherein the isolating membrane has a deflectable working area between a peripheral line (31) defining the intermediate area and the peripheral rim (32), and at least one peripheral bead (19) is provided between the peripheral line (31) and the peripheral rim (32).

9. The diaphragm seal of claim 8, wherein the peripheral adhesive connection is applied between the peripheral line (31) defining the intermediate region and the central recess.

10. Diaphragm seal according to claim 1, wherein the isolating membrane (3) is bonded to the surface (2) of the body (1) in a pressure tight manner by a single peripheral weld.

11. The diaphragm seal of claim 2, wherein the thermally conductive layer is a thermally conductive adhesive layer, a soft solder connection layer, or a thermally conductive paste layer.

12. The diaphragm seal according to claim 5, wherein the insulating material (9) is an insulating material other than air.

13. Diaphragm seal according to claim 8, wherein the peripheral adhesive connection is applied between the peripheral line (31) defining the intermediate region and the central aperture (8).

14. A pressure transducer, comprising:

the diaphragm seal and pressure measurement unit (11) according to any one of claims 1 to 13, which is capable of being subjected to the pressure of the process medium via the hydraulic passage of the diaphragm seal, and an electronic circuit (14) for generating an adjusted pressure-related signal from a main signal of the pressure measurement unit (11).

15. Pressure transducer according to claim 14, wherein the electronic circuit (14) comprises means for processing signals for the temperature measurement variable in the temperature transducer (20).

16. Pressure transducer according to claim 15, wherein the signal of the temperature transducer is applied to an input of a correction circuit (16) for correcting a temperature error of the pressure dependent signal.

17. The pressure transducer of any of claims 14 to 16, wherein the pressure transducer is an absolute pressure transducer, a relative pressure transducer or a differential pressure transducer.